This invention relates to an asymmetric radiant electric heater with multiple heating zones.
Asymmetric radiant electric heaters, for example oval heaters, with multiple heating zones are known, for example, from United Kingdom Patent Publication No. 2,044,057 in which an additional part-circular heated area is arranged to one side of the conventional circular heated area. In practice, the additional part-circular heated area can be arranged either to the left-hand side or to the right-hand side of the circular area. A significant disadvantage of such known oval heaters is that it is necessary to engineer, or tool, the left-hand and right-hand additional areas as separate products. It is also necessary to stock separate components for use in left- and right-handed heaters.
It would result in a significant saving in terms of investment and storage if the same components could be used for both left-and right-handed heaters.
It is therefore an object of the present invention to provide an asymmetric radiant electric heater with multiple heating zones in which the same components can be used for multiple configurations.
According to the present invention there is provided an asymmetric radiant electric heater with multiple heating zones which can be arranged in a plurality of configurations, the heater comprising:
a dish-like support having two orthogonal axes of symmetry;
a base of thermal and electrical insulation material in the dish-like support;
a first heating element and a second heating element supported adjacent one another on a major surface of the base and forming an asymmetric arrangement in the dish-like support;
a terminal block secured at a fixed location at an edge of the dish-like support;
a wall arrangement of thermal insulation material supported on the base and comprising a peripheral wall extending around the heater and a dividing wall, integral therewith, extending between the adjacent first and second heating elements to form at least two asymmetric heating zones;
the wall arrangement being adapted and arranged to cooperate with the base and the terminal block whereby the wall arrangement is fitted to the heater in a first position to accommodate a first configuration of the adjacent first and second heating elements, and in a second position, representing 180 degrees of rotation of the wall arrangement from the first position about an axis perpendicular to a base of the dish-like support, to accommodate a second configuration comprising a mirror image arrangement of the adjacent first and second heating elements.
The dish-like support may be of substantially oval shape.
The first heating element may be of substantially circular configuration with the second heating element being of substantially part-circular configuration.
The dish-like support may have a long axis of symmetry and a short axis of symmetry and the terminal block may be secured at the edge of the dish-like support on the short axis of symmetry. The wall arrangement may have a long axis of symmetry corresponding to the long axis of symmetry of the dish-like support.
The base of thermal and electrical insulation material may be dished. The lower edge of the dividing wall may be profiled to correspond to the dish-shape of the base.
A recess may be provided in the peripheral wall at each end of the dividing wall at a lower edge of the wall arrangement to selectively accommodate electrical connections between the terminal block and one or more of the first and second heating elements.
A protrusion may be provided on the surface of the base of thermal and electrical insulation material directly opposite to where the electrical connections to the terminal block are provided and cooperating with an overlying one of the recesses at the end of the dividing wall to substantially fill such one of the recesses.
A pair of matching elongate projections may be provided directly opposite each other on opposite lower edges of an outer rim of the peripheral wall of the wall arrangement, one of the projections being arranged to bear on the terminal block, the other of the projections being accommodated in a substantially complementary recess provided in the base of thermal and electrical insulation material.
A rod-like temperature-responsive device may be provided at least partly crossing one of the heating zones.
The wall arrangement may comprise bound vermiculite.
The base may comprise microporous thermal and electrical insulation material.
The first heating element and the second heating element may comprise wire, ribbon, foil or film material. In particular, the first heating element and the second heating element may comprise corrugated ribbons supported edgewise on the base of thermal and electrical insulation material.
As a result of the present invention, a standard base component can be provided for a radiant heater, consisting of a dish-like support containing a base layer of insulation material and arranged to be fitted with a terminal block at a fixed symmetrical location. Asymmetric heating elements can be arranged on the base layer in a particular configuration, or a mirror image thereof. A single wall member is provided which, by simple orientation into a selected one of two positions, can be fitted to the base component to accommodate a particular arrangement of asymmetric heating elements, or a mirror image arrangement thereof.